Evaluation of different control measures in 2014 to mitigate the impact of ship emissions on air quality in the Pearl River Delta, China

Various control measures have been proposed to reduce ship emissions. However, improvements in air quality after its implementation have rarely been evaluated on a regional scale. To fill this gap, this study employed the Weather Research and Forecast model coupled with Chemistry (WRF/Chem) model to investigate the improvement in air quality under scenarios separately implementing different control measures. The domestic emission control area (DECA) in the Pearl River Delta (PRD) region of China was selected as the target area for the study. The results suggest that the use of cleaner fuels is a promising way to improve air quality. For vessels sailing in the DECA, using 0.5% sulfur-content fuel could reduce SO₂ and PM_2.5 by 0.52 μg/m³ and 1.43 μg/m³, respectively, in the target cities of PRD, while 0.1% sulfur-content fuel could increase these figures to 0.59 μg/m³ and 1.62 μg/m³, respectively. The use of liquefied natural gas (LNG) fuel was predicted to be the most effective method for air quality improvement. LNG fuel could reduce the annual average concentrations of SO₂, NO₂ and PM_2.5 by 0.63 μg/m³, 2.80 μg/m³ and 2.14 μg/m³, respectively, in the target cities of PRD. The application of shore side electricity (SSE) would reduce the ship-contributed SO₂ and PM_2.5 by 0.33 μg/m³ and 1.06 μg/m³, respectively. For the NO_X control, the retrofit of the selective catalytic reduction (SCR) system could reduce the ambient concentrations of NO₂ and PM_2.5 by 2.09 μg/m³ and 0.15 μg/m³, respectively. These results suggest that the use of cleaner fuels and the retrofit SCR system all have positive effects on lowering the impact of ship emissions, while the application of SSE could be a useful supplement.